e13b4386ff
`abci.Client`:
- Sync and Async methods now accept a context for cancellation
* grpc client uses context to cancel both Sync and Async requests
* local client ignores context parameter
* socket client uses context to cancel Sync requests and to drop Async requests before sending them if context was cancelled prior to that
- Async methods return an error
* socket client returns an error immediately if queue is full for Async requests
* local client always returns nil error
* grpc client returns an error if context was cancelled before we got response or the receiving queue had a space for response (do not confuse with the sending queue from the socket client)
- specify clients semantics in [doc.go](https://raw.githubusercontent.com/tendermint/tendermint/27112fffa62276bc016d56741f686f0f77931748/abci/client/doc.go)
`mempool.TxInfo`
- add optional `Context` to `TxInfo`, which can be used to cancel `CheckTx` request
Closes #5190
KVStore
There are two app's here: the KVStoreApplication and the PersistentKVStoreApplication.
KVStoreApplication
The KVStoreApplication is a simple merkle key-value store.
Transactions of the form key=value are stored as key-value pairs in the tree.
Transactions without an = sign set the value to the key.
The app has no replay protection (other than what the mempool provides).
PersistentKVStoreApplication
The PersistentKVStoreApplication wraps the KVStoreApplication and provides two additional features:
- persistence of state across app restarts (using Tendermint's ABCI-Handshake mechanism)
- validator set changes
The state is persisted in leveldb along with the last block committed, and the Handshake allows any necessary blocks to be replayed. Validator set changes are effected using the following transaction format:
"val:pubkey1!power1,pubkey2!power2,pubkey3!power3"
where pubkeyN is a base64-encoded 32-byte ed25519 key and powerN is a new voting power for the validator with pubkeyN (possibly a new one).
To remove a validator from the validator set, set power to 0.
There is no sybil protection against new validators joining.